Does leucocytosis identify bacterial infections in febrile neonates presenting to the emergency department?

Severe bacterial infection in young infants with pyrexia admitted to the emergency department

The objectives of this study were to understand the clinical presentations of febrile young infants with severe bacterial infection (SBI), and to investigate the pathogen variations throughout the vaccine era and after antenatal group B Streptococcus (GBS) screening.All infants < 90 days old with a body temperature of ≥38.0°C and admitted to the emergency department were retrospectively enrolled in our study. SBI was defined as a positive culture of urine, blood, or cerebrospinal fluid. All clinical variables were analyzed and compared between the SBI group and the non-SBI group, to identify the relevant risk factors for SBI in infants with pyrexia.A total of 498 infants were studied, 279 of whom (56%) had SBI. The body temperature at triage was higher in the SBI group, and the difference was highly obvious in the neonatal group. White blood cell count and C-reactive protein levels were both significantly higher in the SBI group (P < .05), whereas neutrophil percentage and band percentage demonstrated no significant differences. Escherichia coli was the most common pathogen and plasmid-mediated extended-spectrum lactamases were detected in up to 9.1%. GBS was detected in 16 cases of bacteremia (6 cases with concurrent meningitis).The body temperature at triage may provide a clue for differentiating sick babies, especially in the neonatal group. Complete serum analysis is required for infection survey, especially white blood cell and C-reactive protein. Escherichia coli is the most common pathogen, and clinician should raise awareness of drug resistance in some patients. The prevalence of GBS infection in the young infant group remains high after routine antenatal GBS screening.

The relative incidence of cardiogenic and septic shock in neonates

Objective

To evaluate the relative incidence of cardiogenic and septic shock in term neonates and identify findings that help differentiate the two entities.

Study Design

We conducted a retrospective chart review of term neonates presenting to British Columbia Children's Hospital (BCCH) with decompensated shock of an undiagnosed etiology between January 1, 2008 and January 1, 2013. Charts were reviewed to determine the underlying diagnoses of all neonates meeting our inclusion criteria. Patients were categorized as having septic, cardiogenic, or other etiologies of shock. We then evaluated potential demographic, clinical, and biochemical parameters that could help differentiate between septic and cardiogenic shock.

Results

Cardiogenic shock was more common than septic shock (relative risk=1.53). A history of cyanosis was suggestive of cardiogenic shock (positive likelihood ratio, LR+=3.2 and negative likelihood ratio, LR-=0.4). Presence of a murmur or gallop (LR+=5.4, LR-=0.3), or decreased femoral pulses (LR+=5.1, LR-=0.5) on physical exam were also suggestive of cardiogenic shock as was cardiomegaly on chest x-ray (LR+=4.9, LR-=0.5). Notably, temperature instability (LR+=0.7, LR-=1.8) and white blood cell count elevation or depression (LR+=0.8, LR-=1.1) were all poor predictors of septic shock.

Conclusion

Cardiogenic shock is a more common cause of decompensated shock than septic shock. A history of cyanosis, murmur or gallop, or decreased femoral pulses on exam and cardiomegaly on chest x-ray are useful indicators of cardiogenic shock. In evaluating the neonate with decompensated shock, early consideration for Cardiology consultation and interventions to treat the underlying condition is warranted.

Performance of blood biomarkers to rule out invasive bacterial infection in febrile infants under 21 days old

OBJECTIVES

To determine the performance of procalcitonin (PCT), C reactive protein (CRP) and absolute neutrophil count (ANC) in identifying invasive bacterial infection (IBI) among well-appearing infants ≤21 days old with fever without source and no leukocyturia. To compare this performance with that in those 22-90 days old.

DESIGN

Substudy of a prospective single-centre registry performed between September 2008 and August 2017.

SETTING

Paediatric emergency department of a tertiary teaching hospital.

PATIENTS

196 infants ≤21 days old and 1331 infants 22-90 days old.

MAIN OUTCOME MEASURES

Sensitivity and negative likelihood ratio of blood tests for ruling out IBI (positive blood or cerebrospinal fluid culture). Abnormal blood test results: PCT ≥0.5 ng/mL, CRP >20 mg/L and ANC >10 000/µL.

RESULTS

Prevalence of IBI in infants ≤21 days old with normal or any abnormal blood test result was 3.6% and 6.8%, respectively (OR 0.52 (95% CI 0.13 to 2.01)), compared with 0.2% and 4.5% in older infants (OR 0.03 (95% CI 0 to 0.17)). Sensitivity and negative likelihood ratio of the blood tests for ruling out IBI in infants ≤21 days were 44.4% (95% CI 18.9% to 73.3%) and 0.79 (95% CI 0.43 to 1.44), respectively (vs 84.6% (95% CI 57.8% to 95.7%)%) and 0.19 (95% CI 0.05 to 0.67) in older infants). The values improved in infants with fever ≥6 hours aged 22-90 days, but not in those ≤21 days.

CONCLUSIONS

PCT, CRP and ANC are not useful for ruling out IBI in febrile infants ≤21 days old. It is still recommended that these patients are admitted and given empirical antibiotic therapy, regardless of their general appearance or blood test results.

Associations of Neighborhood-Level Social Determinants of Health with Bacterial Infections in Young, Febrile Infants

OBJECTIVE

To examine the sociodemographic characteristics of one population of young, febrile infants and identify associations between neighborhood-level social determinants of health (SDHs) with bacterial infections.

STUDY DESIGN

This was a retrospective cross sectional study of all infants ≤90 days old with a temperature of ≥38°C who presented in 2014 to the emergency department of an urban children's hospital in a large east coast city. The primary outcome was the presence of a bacterial infection, defined as a positive urine, blood, or cerebrospinal fluid culture that was treated clinically as a pathogen. The home address of each infant was geocoded and linked to neighborhood data based on census tract. Neighborhood-level SDHs included deprivation index, median household income, poverty, childhood poverty, social capital, and crowded housing. Associations were estimated using generalized estimating equations and negative binomial regression analysis. Models were adjusted for age, prematurity, and race/ethnicity.

RESULTS

Of 232 febrile infants, the median age was 54 days, 58% were male, 49% were Hispanic, and 88% had public health insurance; 31 infants (13.4%) had a bacterial infection. In the adjusted analyses, the risk of bacterial infection among infants from neighborhoods with high rates of childhood poverty was >3 times higher (relative risk, 3.16; 95% CI, 1.04-9.6) compared with infants from neighborhoods with low rates of childhood poverty.

CONCLUSIONS

Our findings suggest that SDHs may be associated with bacterial infections in young, febrile infants. If confirmed in subsequent studies, the inclusion of SDHs in predictive tools may improve accuracy in detecting bacterial infections among young, febrile infants.

Post-immunization leucocytosis and its implications for the management of febrile infants

Aims

Clinical guidelines for management of infants with fever but no evident focus of infection recommend that those aged 1–3 months with a white cell count >15 × 10⁹/l have a full septic screen and be admitted for parenteral antibiotics. However, there is limited information about leucocyte changes following routine immunization, a common cause of fever. We investigated white cell counts shortly after routine immunization in Ugandan infants under 3 months of age.

Methods

White cell counts were measured in 212 healthy infants following routine immunizations (DTwP-HepB-Hib, oral polio and pneumococcal conjugate 7 vaccines) received prior to 3 months of age.

Results

Mean leucocyte counts increased from 9.03 × 10⁹/l (95% confidence interval 8.59–9.47 × 10⁹/l) pre-immunizations to 16.46 × 10⁹/l (15.4–17.52 × 10⁹/l) at one-day post-immunizations at 6 weeks of age, and 15.21 × 10⁹/l (14.07–16.36 × 10⁹/l) at one-day post-immunizations at 10 weeks of age. The leucocytosis was primarily a neutrophilia, with neutrophil percentages one-day post-immunization of 49% at 6 weeks of age and 46% at 10 weeks of age. White cell parameters returned to baseline by two-days post-immunization. No participant received antibiotics when presenting with isolated fever post-immunization and all remained well at follow-up.

Conclusions

In our study almost half the children <3 months old presenting with fever but no evident focus of infection at one-day post-immunization met commonly used criteria for full septic screen and admission for parenteral antibiotics, despite having no serious bacterial infection. These findings add to the growing body of literature that questions the utility of white blood cell measurement in identification of young infants at risk of serious bacterial infections, particularly in the context of recent immunizations, and suggest that further exploration of the effect of different immunization regimes on white cell counts is needed.

This observational work was nested within a clinical trial, registration number ISRCTN59683017.

Principles of Use of Biostatistics in Research

Collecting, analyzing, and interpreting data are essential components of biomedical research and require biostatistics. Doing various statistical tests has been made easy by sophisticated computer software. It is important for the investigator and the interpreting clinician to understand the basics of biostatistics for two reasons. The first is to choose the right statistical test for the computer to perform based on the nature of data derived from one's own research. The second is to understand if an analysis was performed appropriately during review and interpretation of others' research. This article reviews the choice of an appropriate parametric or nonparametric statistical test based on type of variable and distribution of data. Evaluation of diagnostic tests is covered with illustrations and tables.

Diagnostic markers of serious bacterial infections in febrile infants younger than 90 days old

BACKGROUND

The aim of this study was to assess correlations between demographic, clinical and laboratory characteristics and the risk of serious bacterial infection (SBI) in febrile <90-day-old infants.

METHODS

Medical records of all infants younger than 90 days old hospitalized at Dana-Dwek Children's Hospital (2006-2008) for evaluation of fever were retrospectively reviewed. Data on clinical, laboratory and demographic characteristics were retrieved and evaluated.

RESULTS

Forty-eight of the 401 study infants (12%) had SBI: most of them had urinary tract infection (43 infants; 90% of all SBI), three infants had bacteremia, one had bacterial pneumonia and one had bacterial meningitis. Significant independent clinical predictors for the diagnosis of SBI included duration of fever, absence of rhinitis and the absence of lung and skin manifestations. Significant independent laboratory predictors were absolute neutrophil count (ANC), platelets, blood urea nitrogen and C-reactive protein (CRP) level. On receiver operating characteristic curve analysis, the CRP area under the curve (0.819) was significantly superior to ANC and leukocyte count.

CONCLUSION

Of the clinical and laboratory variables selected for evaluation, qualitative CRP was the strongest independent predictor for diagnosing SBI and a significantly better diagnostic marker than clinical characteristics, ANC and white blood cell count.

Hyperleukocytosis in newborn: a diagnosis of concern

Leukocytosis is well recognised in neonate; mostly it is physiological but the counts rarely exceed 30,000/mm(3). Hyperleukocytosis defined as WBC count of more than 100,000 mm(3) is rare and imposes a diagnostic challenge and should be investigated for leukaemia, leukocyte adhesion defect and myeloproliferative disorders. We report a classic case to highlight this entity.

Should complete blood count be part of the evaluation of febrile infants aged ≤2 months?

OBJECTIVE

To determine the utility and importance of total white blood cell count (WBC) and absolute neutrophil count (ANC) as markers of serious bacterial infection (SBI) in hospitalized febrile infants aged ≤2 months.

PATIENTS AND METHODS

Data on WBC and ANC were collected prospectively for all infants aged ≤2 months who were hospitalized for fever at our centre. The patients were divided into two groups by the presence or absence of SBI.

RESULTS

A total of 1257 infants met the inclusion criteria, of whom 134 (10.7%) had a SBI. The area under the ROC curve was 0.73 (95% CI: 0.67-0.78) for ANC, 0.70 (95% CI: 0.65-0.76) for %ANC and 0.69 (95% CI: 0.61-0.73) for WBC. The independent contribution of these three tests in reducing the number of missed cases of SBI was significant.

CONCLUSION

Complete blood cell count should remain as part of the routine laboratory assessment in this age group as it is reducing the number of missing infants with SBI. Of the three parameters, ANC and %ANC serve as better diagnostic markers of SBI than total WBC. However, more accurate tests such as C-reactive protein and procalcitonin should also be part of the evaluation of febrile infants in these age group as they perform better than WBC or ANC for predicting SBI.

C-reactive protein as a marker of serious bacterial infections in hospitalized febrile infants

OBJECTIVE

To determine the potential predictive power of C-reactive protein (CRP) as a marker of serious bacterial infection (SBI) in hospitalized febrile infants aged < or =3 months.

PATIENTS AND METHODS

Data on blood CRP levels were collected prospectively on admission for all infants aged < or =3 months who were hospitalized for fever from 2005 to 2008. The patients were divided into two groups by the presence or absence of findings of SBI.

RESULTS

A total of 892 infants met the inclusion criteria, of whom 102 had a SBI. Mean CRP level was significantly higher in the infants who had a bacterial infection than in those who did not (5.3 +/- 6.3 mg/dL vs. 1.3 +/- 2.2 mg/dL, p < 0.001). The area under the ROC curve (AUC) was 0.74 (95% CI: 0.67-0.80) for CRP compared to 0.70 (95% CI: 0.64-0.76) for white blood cell (WBC) count. When analyses were limited to predicting bacteremia or meningitis only, the AUCs for CRP and WBC were 0.81 (95% CI: 0.66-0.96) and 0.63 (95% CI: 0.42-0.83), respectively.

CONCLUSION

C-reactive protein is a valuable laboratory test in the assessment of febrile infants aged < or =3 months old and may serve as a better diagnostic marker of SBI than total WBC count.

Serious bacterial infections in febrile infants in the post-pneumococcal conjugate vaccine era

OBJECTIVES

The objective was to identify the epidemiology of serious bacterial infections (SBI) and the current utility of obtaining routine complete blood counts (CBC) and blood cultures to stratify infants at risk of SBI, in the study population of febrile infants in the post-heptavalent pneumococcal conjugate vaccine (PCV7) era.

METHODS

A cohort study with nested case-controls was undertaken at a tertiary care military hospital emergency department (ED) from December 2002 through December 2003. Irrespective of clinical findings at the initial encounter, patients were included if they were under 3 months of age and had a home or ED temperature of >or=100.4 degrees F or if they were between 3 and 24 months of age with a temperature of >or=102.3 degrees F. Data abstracted included age, temperature, peripheral white blood cell (WBC) count, and discharge diagnosis. Culture (blood, urine, and cerebrospinal fluid [CSF]) and chest radiograph (CXR) results were obtained through review of the electronic hospital archives. SBI was defined as pneumonia, urinary tract infection (UTI), meningitis, or bacteremia.

RESULTS

A total of 985 children aged 0 to 24 months were enrolled. Fifty-five percent were male, the median age was 12 months (interquartile range = 8-17 months), and 79% had received at least one PCV7. A total of 132 cases of SBI were identified in 129 infants (13.1%): 82 pneumonias, 45 UTI, five bacteremias, and no cases of bacterial meningitis. The frequency of bacteremia was 0.7%. No statistical difference was detected in the WBC count between the SBI and non-SBI groups (13.8 +/- 5.8 and 11.7 +/- 5.6, respectively; p = 0.055). No readily available WBC cutoff on the receiver operating characteristic (ROC) curve proved to be an accurate predictor of SBI. No statistical difference was detected in mean temperature between the SBI and non-SBI groups (103.3 +/- 1.2 and 103.2 +/- 1.2 degrees F, respectively; p = 0.26), nor was there a difference noted when groups were broken down by age or height of fever.

CONCLUSIONS

The WBC count and height of fever were not found to be accurate predictors of SBI in infants age 3 to 24 months. UTI and pneumonias made up the vast majority of SBI in this population of infants. The overall bacteremia frequency was well below 1%. This calls into question the continued utility of obtaining routine complete cell counts and blood cultures in the febrile infant in the post-PCV7 era.

Understanding diagnostic tests 3: Receiver operating characteristic curves

The results of many clinical tests are quantitative and are provided on a continuous scale. To help decide the presence or absence of disease, a cut-off point for 'normal' or 'abnormal' is chosen. The sensitivity and specificity of a test vary according to the level that is chosen as the cut-off point. The receiver operating characteristic (ROC) curve, a graphical technique for describing and comparing the accuracy of diagnostic tests, is obtained by plotting the sensitivity of a test on the y axis against 1-specificity on the x axis. Two methods commonly used to establish the optimal cut-off point include the point on the ROC curve closest to (0, 1) and the Youden index. The area under the ROC curve provides a measure of the overall performance of a diagnostic test. In this paper, the author explains how the ROC curve can be used to select optimal cut-off points for a test result, to assess the diagnostic accuracy of a test, and to compare the usefulness of tests.

CONCLUSION

The ROC curve is obtained by calculating the sensitivity and specificity of a test at every possible cut-off point, and plotting sensitivity against 1-specificity. The curve may be used to select optimal cut-off values for a test result, to assess the diagnostic accuracy of a test, and to compare the usefulness of different tests.

Fever without source in children 0 to 36 months of age

Although fever in the young child (0-36 months) is a common clinical problem, the evaluation and treatment of febrile children remain controversial. Furthermore, universal vaccination with the heptavalent pneumococcal conjugate vaccine (PCV7) has changed the epidemiology of invasive bacterial disease in young children. This article addresses the approach to febrile neonates (0-28 days old), young infants (1-3 months old), and older infants and toddlers (3-36 months old) in the PCV7 era.